THE WILD WEST: Dead Men's Tales
Troopers who fell at the Battle of Little Bighorn in 1876 left clues to their identity deep in their bones, clues that could not be read until more than 100 years later. Now, thanks to hi-tech detecting, some soldiers can be identified. As you will see on Frontiers, although scientists can solve some of the mysteries by clues left at the battlefield, tracking down identities requires dedicated forensics work from many sources, including a dentist and an anthropologist.
Activity 1: DNA Detective
For Further Thought
Native American culture,
ACTIVITY 1: DNA DETECTIVE
Analysis of human skeletal remains has become an invaluable research tool to the forensic pathologist. With the development of various DNA isolation and analysis techniques, identification is much more certain, even if not as artistic and hi-tech as a facial reconstruction.
While the full procedures of DNA testing and fingerprinting are not possible in most school laboratories, DNA can be isolated from onions, bacteria and yeast in most labs for a low cost. Here is a procedure you can try for yourself to isolate DNA from onion cells. You will prepare a solution, then heat, chill, blend, chill, filter and precipitate the DNA.
- cheesecloth or number 6 coffee filter
- a medium-sized onion
- ice for ice-water bath
- test tubes or graduated cylinders
- beakers of various sizes
- stirring rod or pipette
- deionized or distilled water
- lab thermometer
- 30mL dishwashing detergent or shampoo (Alberto VO-5) or 10g sodium dodecyl
- sulfate powder (SDS)
- 3g EDTA (ethylenediamine tetraacetic acid)
- 20mL ethanol, 95 percent (keep cold in test tube on ice)
- 9g sodium chloride (preferably non-iodized)
- In a large beaker mix 9g sodium chloride, 3g EDTA and 30mL detergent or shampoo. Dilute to 1000mL with deionized water to form the homogenizing solution.(NOTE: When onions are added to this solution, the salt attaches to the free ends of the DNA and keeps them from combining with other molecules when the cells are disrupted. The EDTA causes the other cell material to clump together and be removed by precipitation. The detergent or shampoo is a source of SDS, a surfactant that will help break down the cell membranes of the onion cells. Using 10g of pure SDS powder instead of detergent will create less foaming in Step 4.)
- Dice the onion into very small pieces, put into a beaker and add enough of the homogenizing solution from Step 1 to cover the onion. You might pack the diced onion before adding the solution. Then incubate in a hot-water bath at 600C for 15 to 20 minutes. (Make the water bath in a styrofoam ice chest by adding hot water to maintain the temperature. Do not allow the temperature to go much higher or the DNA will denaturize; i.e., the two side strands will separate.)
- Quickly cool the beaker containing the onion homogenate to 150 to 200C in an ice-water bath or freezer to aid precipitation of cellular components in the next step.
- Pour the cooled homogenate into a blender. Blend until the onion is a pulpy mass; excess suds will form if blended too long.
- Pour the cooled homogenate into a large beaker and further cool in an ice-water bath for 15 minutes. This will allow precipitation of cellular components and some of the foam will disappear.
- Filter the homogenate through four layers of cheesecloth or a coffee filter into a clean beaker, leaving as much of the foam behind as you can.
- Transfer 10mL of the filtered onion homogenate into a test tube or graduated cylinder.
- DNA precipitation: Trickle approximately 20mL of ice-cold 95 percent ethanol down the sides of the test tube or cylinder containing the homogenate. Keep the tube on ice if possible. In a few minutes, you should see a white, mucous-like layer forming at the boundary between the alcohol and the filtrate solution. This is onion cell DNA!
- Using a very clean glass stirring rod (or heat and draw out the end of a glass pipette into a thin tube with a hook on the end), gently spool the DNA onto the end of the rod or pipette tip. Save it in 95 percent ethanol and examine under a microscope.
- Test the solution with a good acid/base indicator to demonstrate the acidity of the DNA layer.
(NOTE: You can do this lab in one class period with your students, if you have prepped everything in advance. Have the onion filtrate ready to use and chilled and the ethanol chilled. Or, take one class period to prepare the filtrate, allow to chill overnight and do the DNA precipitation the next class period (process takes about 15 minutes). Some teachers prefer to do the prep ahead and have students work with the filtrate and alcohol solutions only.
Just as recipes have many variations, so do some lab experiments. Some teachers prefer the cookbook approach, but others prefer to adapt and experiment with different ingredients and amounts, which you can do with this lab.
With this lab, it is critical to keep the tube of onion filtrate and the ethanol solution ice-cold. It's recommended that you keep the test tube with the DNA precipitate sitting in a beaker of ice; keep the ethanol on ice the entire time it is not being poured. You will need at least twice as much ethanol as filtrate for the precipitate to occur.)
- How might DNA testing of the skeletal remains from Little Bighorn change or modify the conclusions scientists demonstrated on Frontiers?
- What do scientists hope to find out by DNA testing of troopers' remains? What would they need to make a positive ID?
- If someone in your family has a disease you might inherit, would you choose to have your DNA tested? Would you want to know the results? Who should have the right to access this information besides yourself? Your family? Your employer? Your insurance company? What legal rights should you have to your own DNA information?
- Investigate the use of EDTA in the crime lab as presented in the Simpson trial. EDTA, a preservative and anticoagulant used in police labs to prevent chemical degradation of samples, is also found in many foods and home cleaning products.
- Dry the DNA and dissolve in a TBE buffer and use restriction enzymes to cut the DNA and run it on an agarose gel electrophores device if available.
- In the summer of 1995, DNA testing was done on another legendary figure from the "Wild West," Jesse James. Scientists exhumed the remains to see if the person buried was indeed James. In this technique of DNA analysis, mitochondrial DNA (inherited only from the mother) will be compared with DNA in James's living descendants. At press time, results were not yet known.
- Investigate how forensic analysis using DNA fingerprinting is done. A good reference is DNA on Trial: Genetic Identification and Criminal Justice by Paul R.
Billings (Cold Spring Harbor Laboratory Press, 1992).
- Explore other uses for DNA isolation and analysis techniques in the areas of genetic testing for disease, gene therapy or the Human Genome Project.
- Investigate the use of DNA tests on the remains of Zachary Taylor, hair samples from Abraham Lincoln and bone samples of the Romanovs, currently being compared with DNA from Prince Philip.
FOR FURTHER THOUGHT
- Why did General George Custer decide to fight at Little Bighorn?
- What were the attitudes toward Native Americans at the time of the battle?
- What happened to the Sioux and Cheyenne after Little Bighorn?
- For more on Gen. George Custer, read Son of the Morning Star by Evan S. Connell (Harper & Row, 1984) or see the movie of the same name.
- For another perspective, read Custer's Fall: The Indian Side of the Story by David H. Miller (U. of Nebraska Press, 1957).
Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.